This application claims the priority of 196 30 014.2, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to an automatically controlled clutch which is arranged between the engine and the driving wheels in the transmission line of a motor vehicle having a transmission which can be shifted arbitrarily and manually between idling and driving positions. A control device operates a clutch actuating assembly as a function of given parameters sensed by an assigned sensing system.
Motor vehicles having automatic clutches are known and are produced as standard models. In comparison to vehicles having a clutch to be operated by the driver, an increased comfort is offered. In combination with conventional, manually shifted mechanical transmissions, only extremely low power losses must be accepted in the driving operation so that also comparatively low-power vehicles can be used with automatic clutches. The operating performance of the known automatic clutch is subjected to constant changes which are caused, for example, by changing temperatures as well as setting and wear phenomena. An object of the invention to ensure an operating performance of the automatic clutch which is as constant as possible.
According to the present invention, this object achieved by providing that the signals of the sensing system reflect the actuating path of the actuating assembly as well as the torque of the engine, and indicate whether the vehicle is stopped, whether the service brake is operated and whether a or which driving position is engaged. A control device sets the clutch, while the vehicle is stopped and the driving position is simultaneously engaged and the service brake is operated, at least temporarily to its present gripping point and stores an adapted gripping point actuating stroke which corresponds to the previous gripping point actuating stroke plus a given larger fraction of the deviation between the previous gripping point actuating stroke and the actuating stroke which occurred during the setting of the present gripping point.
The present invention is based on the concept of letting the control device operate with a continuously adapted gripping point actuating stroke so that the control device "knows" sufficiently precisely when the clutch starts to grip during the engaging or has almost opened during the disengaging. During the adaptation according to the present invention it is, on one hand, it is also account that, particularly as a result of temperature influences, fairly large changes of the gripping point actuating stroke may occur relatively frequently. On the other hand, it is also taken into account that the direction of the changes can be altered. In that now, during the adaptation, in each case, only a fraction, for example, half of the deviation between the previously stored gripping point actuating stroke and an actually implemented gripping point actuating stroke is taken into account, a fast adaptation can be achieved during changes of the gripping point position with an alternating direction as well as during changes with a constant direction. As a result, the respective stored gripping point actuating stroke is situated in a narrow tolerance band close to the optimum.
According to a currently preferred embodiment of the present invention, the control device stores continuously adapted data which reflect the dependence of the torque transmitted by the clutch on the actuating stroke of the actuating assembly. That is, the control device therefore "knows" the characteristic curve between the actuating stroke and the clutch torque. This characteristic curve is essentially determined by its gradient (slope) as well as by the position of the gripping point.
According to the present invention, the gradient can be determined during the change of a driving position and the resulting automatically occurring engaging and disengaging of the clutch because the torque transmitted by the clutch is determined by the torque generated by the engine as well as the time variation of the rotational speed of the engine. If now, during a change of the actuating stroke, the torque of the engine as well as the time variation of the rotational speed of the engine are recorded, a value can in each case be determined for the above-mentioned gradient.
The present invention allows an adaptation here to be carried out which is similar to that of the gripping point determination. The adapted value of the gradient to be stored will then in each case correspond to the last-stored value of the gradient plus a given larger fraction of the deviation between the actual value of the gradient and the previously stored value. In this manner, when controlling the clutch, the control device can continuously take into account an updated characteristic curve between the actuating stroke and the clutch torque.